Sakon Nakhon is a Buddhist town with five Buddhist stupas. Its history can be dated back for three thousand years.
Legend says that Nongharn town, or presently Sakon Nakhon, was built in 11th century when Khmer ruled this region. When the Khmer lost their power, the town was under the rules of Lanxang or Laotian Kingdom. It was renamed “Muang Chiang Mai Nongharn”. When the town was under the Siamese Kingdom, it was renamed again into “Sakon Thavapi”. In 1830, during the reign of King Rama III, it was named “Sakon Nakhon”.
About language... mix of Thai and Lao is spoken in Sakon Nakhon; however, plain old Central Thai is perfectly acceptable. There are few expats living in the city or foreign visitors so don't expect much in the way of spoken English or English translations beyond road signs. That being said it's advisable to dive head-first into learning the dialect and start mixing it up with the locals.